Question about upgrading RAM on Nehalem Quad-core 2.66

I know there have been RAM questions here, but I haven't found one that specific to my question....CLOSE...but I just wanna be sure.

Q: I bought a Nehalem Quad-core 2.66. I understand I am able to purchase 4GB Ram chips for my machine(up to four of them). Here's my question...My machine came with 3x1GB Ram. I want to purchase 2x4GB and keep two of the 1GB chips, so that my resulting configuration will be 2x4GB, 2x1GB.

Is this possible? Is this allowed?
I ask this because several websites I've been to only offer the 4GB chips in clusters of either 1's, 3's, and 4's.....somebody please set me straight. I don't wanna waste my money if my 2x4/2x1 plan isn't possible.

OWC p/n OWC8566D3MPE4GB 4GB modules require that all installed modules be of this same matching part. Other existing Apple or 3rd party 1GB, 2GB and 4GB modules are not supported for use with this kit and need to be removed when this kit is added.

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I would check with the vendors you're thinking of using, but I suspect mix 'n' match won't work.

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I ask this because several websites I've been to only offer the 4GB chips in clusters of either 1's, 3's, and 4's.....somebody please set me straight. I don't wanna waste my money if my 2x4/2x1 plan isn't possible.

Cheers!

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Also had a look at Crucial and it offers 8GB (2x4GB modules) but it's a lot more expensive than OWC. Doesn't say anything about not mixing modules, so probably fine.

I was in the same boat about a month ago with my quad nehalem and this it what I worked out. I ended up going with this server memory over at newegg, (its since gone up about 40$) and its worked great. There were some questions I had about heat sensors, etc, but there have been absolutely no problems and the memory works great.

Here's where we can maybe help each other out. (or if anyone else is interested). I do some heavy after effects work and still find myself running out of RAM on larger renders, so I am looking to get one more 4gb stick to bump my system to 16gb total. They don't sell that ram in singles, but if you wanted to split a three pack, (2 for you, 1 for me), then you'd have your 2x4gb 2x1gb setup and I'd get my last slot filled (sounds a bit dirty). Sucks that it kicks the ram down to dual channel, but still infinitely faster than running out of ram and swapping to the hard drive.

BTW - they also offer two packs of the 4gb sticks for slightly more per stick.

I was in the same boat about a month ago with my quad nehalem and this it what I worked out. I ended up going with this server memory over at newegg, (its since gone up about 40$) and its worked great. There were some questions I had about heat sensors, etc, but there have been absolutely no problems and the memory works great.

Here's where we can maybe help each other out. (or if anyone else is interested). I do some heavy after effects work and still find myself running out of RAM on larger renders, so I am looking to get one more 4gb stick to bump my system to 16gb total. They don't sell that ram in singles, but if you wanted to split a three pack, (2 for you, 1 for me), then you'd have your 2x4gb 2x1gb setup and I'd get my last slot filled (sounds a bit dirty). Sucks that it kicks the ram down to dual channel, but still infinitely faster than running out of ram and swapping to the hard drive.

BTW - they also offer two packs of the 4gb sticks for slightly more per stick.

Cheers.

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You should only lose about 25% bandwidth performance with 4 DIMMs over 3. The benchmarks for Mac Pros out there with full DIMMs vs triple channel are all with unbuffered memory which has a further performance decrease when running more than 1 DIMM on any channel. This doesn't happen with the Registered memory you are using. So even though Apple don't support it anyone filling all DIMM slots should be using registered memory for extra bandwidth.

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